TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

How much 12v current is available?

Discussion in 'Model S: Battery & Charging' started by AB4EJ, Mar 5, 2015.

  1. AB4EJ

    AB4EJ Member

    Joined:
    Feb 25, 2015
    Messages:
    584
    Location:
    Tuscaloosa, AL
    I am into amateur (ham) radio. If I would like to install a 2-way radio in a Model S...

    Would there be 15 amps of 12-v available to power that radio while it is transmitting?

    Would the 50 watts of RF coming out of the antenna pose a significant risk to the very complex Model S electronics? (typically 144 mHz band)

    Does anyone have definitive (i.e., based on known facts rather than speculation) answers?
     
    • Like x 1
  2. jgs

    jgs Member

    Joined:
    Oct 28, 2014
    Messages:
    951
    Location:
    Ann Arbor, Michigan
    The 6.0 manual (p. 80) says "The 12V power socket is suitable for accessories requiring up to 15A or a maximum of 180 watts."

    I doubt you'll find anyone able to answer your second question based on known facts rather than speculation -- even aircraft manufacturers don't seem to be able to provide definitive answers to such questions. If the car is susceptible to failure due to a 50 watt RF source nearby though, I'll be VERY disappointed.
     
  3. scottm

    scottm Active Member

    Joined:
    Jun 13, 2014
    Messages:
    1,277
    Location:
    Canada
    Curious where/how you would mount the antenna. Maybe placement matters. There are antennae all over the car for its purposes.
     
  4. AB4EJ

    AB4EJ Member

    Joined:
    Feb 25, 2015
    Messages:
    584
    Location:
    Tuscaloosa, AL
    This might have been tried

    THANKS for the info on the current availability.
    Regarding RF susceptibility - I worked as an engineer for GM years ago, and we had some RF chambers where we would bombard a running car (on the dyno) with all kinds of RF, to see what would affect it, and how. At the time, it took quite a strong RF field to affect a vehicle (way more than a typical ham mobile rig would produce); but the Tesla seems to have a lot more electronics than the cars I worked with. I was thinking that probably somebody has tried this and could provide actual test results.

    - - - Updated - - -

    There are a couple of options. Several types of antenna are available with mounts to the trunk lid. Brave souls also will use heavy mag-mounts (risk here is scratching the paint). But what I really hope to do is to get a Model X with the trailer hitch; there are inserts that will let you put the antenna on the trailer hitch, with a tennis ball to help cushion it from banging into the back of the car.
    Placement is a minor consideration. In the past, when I had a cheap car, I would drill through the roof and put a commercial antenna mount on, like on a police car or taxi, - this will give you your best RF pattern; but I wouldn't do this with a high end car - too much loss of value from the body damage. For casual use, you can mount an antenna almost anywhere; the car has enough metal mass to create your ground plane.
     
  5. NigelM

    NigelM Recovering Member

    Joined:
    Apr 3, 2011
    Messages:
    13,257
    Location:
    Sarasota, FL
    You know the whole bodywork on Model S is aluminum...
     
  6. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    There are a couple of other things to note, if you don't want to use the lighter/accessory outlet. The nosecone terminals will give you up to 50A of current (it's protected with a dedicated fuse). However, you also have to mind the voltage... the Model S voltage can vary between 12 volts (static battery voltage, all powered down) and 15.1 volts (rapid charge cycle for the AGM 12V battery). Most equipment is built to survive this, but you should check.

    - - - Updated - - -

    The bumper and B-pillar have steel!
     
    • Like x 1
  7. saladman

    saladman Member

    Joined:
    Feb 11, 2015
    Messages:
    95
    Location:
    Seattle, WA
    My intentions are to install the base unit of a Kenwood 700 in the Frunk, leaving me to install the faceplate in the interior. This should give me access to the battery terminals up front, leaving the 12v adapter free. And then a lip mount for the antenna on the back hatch.

    The 2011 Nissan Leaf was not susceptible to any interference that I could find.

    I've never drilled any of my cars for a radio install. Certainly not going to start here. :)

    Any Ham Radio Operators in the group? VHF mobile installation query? | Forums | Tesla Motors

    Amateur radio in a Model S | Forums | Tesla Motors

    Any amateur radios in a Model S yet? | Forums | Tesla Motors

    Solution for amateur radio operators? Impossible to use magmount antennas in a Tesla
     
  8. NigelM

    NigelM Recovering Member

    Joined:
    Apr 3, 2011
    Messages:
    13,257
    Location:
    Sarasota, FL
    Not sure either of those is good for a mag mount antenna! :p
     
  9. herbvdh

    herbvdh Member

    Joined:
    Jan 31, 2010
    Messages:
    200
    Has anyone had any success installing a 2 Meter 440 Amateur Radio yet??? K2VDH I have heard that some Ambulance Squad member installed there Radio's but never found any solid info out.
     
  10. AB4EJ

    AB4EJ Member

    Joined:
    Feb 25, 2015
    Messages:
    584
    Location:
    Tuscaloosa, AL
    Diamond makes an antenna that can bolt (without drilling holes) to a typical trunk lid, so it would likely work on the MS hatch. Earlier in this thread, it is reported that plenty of current is available at the 12v battery terminals, but due to the fast charge circuit, it might be necessary to include a regulator in the circuit to protect the radio (these are readily available).
     
  11. TaoJones

    TaoJones Beyond Driven

    Joined:
    Nov 10, 2014
    Messages:
    1,299
    Location:
    The Americas
    One can also draw from the battery (unswitched) via a dedicated connection with a (e.g., 15A fuse). Please keep in mind that the 12V console source is switched, meaning that it will shut off 30 minutes after the "Car Off" message appears.
     
  12. Oba

    Oba Member

    Joined:
    Jun 7, 2015
    Messages:
    234
    Location:
    SoCal
    The DC to DC converter is rated at 100 amps, therefore you could make a fused dedicated lime from the 12 volt battery to power your equipment.

    What you need to know is how much power is actually available out of that 100 amps. Put an ammeter on the 12 volt battery, turn everything on (radio blasting, heater fan on full blast, all lights on, etc) and see what's actually burnt.
     
  13. mspohr

    mspohr Active Member

    Joined:
    Jul 27, 2014
    Messages:
    1,797
    Location:
    California
    Aluminum works as well as steel for a ground plane. It does not need to be magnetic, just conductive.
     
  14. markn455

    markn455 Member

    Joined:
    Apr 8, 2016
    Messages:
    207
    Location:
    Ball Ground, GA
    Where are the Nosecone Terminals located?
     
  15. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    If you pop the nosecone off the front of the car, you will find a 12V positive terminal. search for "inverter in the frunk".
     
  16. TaoJones

    TaoJones Beyond Driven

    Joined:
    Nov 10, 2014
    Messages:
    1,299
    Location:
    The Americas
    Have they not moved the location of that terminal in later models?
     
  17. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    Perhaps. I drive one of the classics, so I only know where mine is.

    In the Model X it's now underneath the cover at the back of the frunk.
     
    • Helpful x 1

Share This Page